Modern mobile platforms have constantly increasing power demands. Platforms will require more power supplies, i.e. regulators, to supply different functions in the platform. Granularity in power supply usage is required to optimize efficiency, as load currents may be high. Thus supply voltage should preferably be optimised in order to avoid any efficiency loss. Eventually, more and more regulators are required to achieve good battery life time for future mobile electronic products. Often regulators are Switched Mode Power Supplies (SMPS) which achieves good efficiency. If all power supplies in a platform are concentrated to a single Integrated Circuit (IC), location of the SMPS on the Printed Circuit Board (PCB) might be non-optimum versus the load location. Further, thermal heating might become too excessive for one IC to sustain. Thus, a solution is to add more and more regulator ICs, i.e. more and more ICs that each comprises one or more regulators such as one or more SMPS, to the mobile platform. However, with many regulator ICs it becomes more complex to control all the regulators, especially taking into account that regulators are typically controlled and enabled during boot up sequence when platform Soft Ware (SW) is not yet in charge of the regulator control. Further, it is important that regulators are enabled and disabled in certain specific orders. Start-up order is important in order to guarantee platform functionality but also to avoid all SMPS to activate simultaneously with excessive momentary battery currents as a result.
Even if two similar regulator ICs would be enabled exactly at the same time point, they could enable their one or more regulators at different times because the time base in each regulator IC varies. The reason for that is typically that, due to cost reasons, low precision oscillators are used in the regulator ICs in order to take care of the time base. In a mobile platform this could lead to a misaligned rank sequence and cause malfunctioning of the mobile platform.
In case a plurality of ICs is present in the mobile platform, one of the ICs is normally defined to be a master circuit, while the other circuits are defined to be slave circuits. The master circuit controls the power-up and power-down of the entire system. This may be realized with an enable signal which is controlled by the master circuit and which can be detected by the slave circuits. Whenever the enable signal becomes active, the slave circuits cause the associated functional components to be powered up, and whenever the enable signal becomes inactive, the slave circuits cause the associated functional components to be powered down.
U.S. Pat. No. 7,395,440 B2 relates to an electronic device comprising at least two power management circuits and a signal line connecting the circuits. Each of the circuits is adapted to control a power supply to at least one functional component of the electronic device. Each of the circuits is adapted to detect a condition which requires powering down functional components of said electronic device and to set the signal line to a predetermined state, in case the circuit detects a condition which requires a powering down of the electronic device. Further, each of the circuits is adapted to monitor a state of the signal line and to power down all functional components associated to it upon detection of the predetermined state of the signal line.
US 2004/0227404 A1 discloses that power supplies, supplied with an input voltage to produce output voltages, are controlled in a desired sequence, and their output voltages are monitored, by respective state machines of two or more control units which are coupled in cascade by a bidirectional path on which commands and acknowledgements are coupled serially in frames.
A drawback with the prior art is that they don't provide simultaneous power control of a plurality of power units.